Characterization and comparative analysis of three low molecular weight glutenin C-subunit genes isolated from Aegilops tauschii

Three low molecular weight glutenin subunit (LMW-GS) genes from T121, T128 and T132 accessions of Aegilops tauschii (DD, 2n = 2x = 14) were amplified using allelic-specific PCR primers. The amplified products with a size of about 900 bp were cloned and sequenced. Three complete coding sequences of LMW-GS with 918 bp, 921 bp and 918 bp were obtained and named as LMW-T121, LMW-T128, LMW-T132, respectively. Each gene contained a complete open reading frame and had no introns. The deduced amino acid sequences showed that all belonged to LMW-m type subunit with a predicted molecular weight of about 32 kDa, corresponding to the size of LMW C-subunits. All three subunits possessed eight cysteine residues and had greater homology with previously characterized LMW-m subunits from bread wheat and related species than LMW-s or LMW-i sequences. Some amino acid substitutions and insertion/deletion variations among the sequences were detected. The corresponding three C-subunits in seed endosperm encoded by LMW-T121, LMW-T128, LMW-T132, respectively, were identified and confirmed by SDS-PAGE, MALDI-TOF-MS and direct N-terminal amino acid sequencing. Phylogenetic analysis demonstrated that LMW-m and LMW-s type subunit genes possessed higher identity and they were obviously separated from LMW-i type subunit genes. The LMW-m type might be the primitive form while the LMW-s and LMW-i types are variant forms.